New
New
Identify properties of triangles
I can use different properties to identify and sort triangles.
Lesson 4 of 10
New
New
- Year 3
Identify properties of triangles
I can use different properties to identify and sort triangles.
Lesson details
Key learning points
- Triangles always have three sides, vertices and angles.
- Triangles always have straight sides and sharp vertices.
- Triangles can have right angles.
- Vertices are the corners of a shape.
Keywords
Triangle - A polygon with three straight sides.
Vertex - The point where two lines meet.
Vertices - More than one vertex.
Properties - A character or quality that something has.
Common misconception
Pupils may see other shapes and collections of lines as triangles when they are not (e.g. shapes with rounded corners, three lines that do not all meet).
Provide pupils with shapes, and explore shapes in the environment, classifying them as 'triangles' and 'not triangles'. Ask children, 'Does this shape have three straight sides? Does it have clearly defined, sharp vertices?'
Pupils will already have some familiarity with triangles but this lesson helps them to define what a triangle is. Pupils begin to classify and sort triangles by their angles, length of sides and whether they have reflective symmetry or not. The sorting provides opportunities for pupil discussion.
Teacher tip
Licence
This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which of these images shows a right angle?
Which of these images shows a right angle?
b
c
Q2.A right angle is the same as a turn.
A right angle is the same as a turn.
half
three-quarter
whole
Q3.How many right angles does this shape have?
How many right angles does this shape have?
1
2
3
Q4.Look at this triangle. Which of these statements are true?
Look at this triangle. Which of these statements are true?
The shape has 2 lines of symmetry.
The shape has 3 lines of symmetry.
Q5.Which letter does not have at least one right angle?
Which letter does not have at least one right angle?
E
H
T
Q6.Which shapes have at least one right angle?
Which shapes have at least one right angle?
a
c
d
Assessment exit quiz
6 Questions
Q1.The corners of a shape are called the .
The corners of a shape are called the .
properties
symmetry
right angles
Q2.Which of these shapes are triangles?
Which of these shapes are triangles?
b
c
Q3.Which of these statements are true for all triangles?
Which of these statements are true for all triangles?
They have 3 rounded vertices.
They have two sides the same length.
Q4.Which triangle is exactly the same size and shape as shape a)?
Which triangle is exactly the same size and shape as shape a)?
b
c
e
Q5.Which triangles have one right angle?
Which triangles have one right angle?
c
d
Q6.Which triangles have at least two sides the same length?
Which triangles have at least two sides the same length?
a
c
